a. Field of the Invention
The instant invention relates to assemblies and methods for puncturing, or piercing, tissue within the body, including, for example, transseptal access systems and methods for accessing the left atrium from the right atrium by crossing the fossa ovalis. In particular, the instant invention is directed toward medical devices used with catheter assemblies in cardiology procedures that require tissue punctures, or piercings, such as transseptal punctures. More specifically, the instant invention relates to improved hand assemblies and methods combining a number of the separate devices used in transseptal catheterization procedures, including sheaths, dilators, and needle assemblies (including a puncture device and a stylet, for example). The hand assemblies provide cooperating members that reduce the overall complexity and increase safety of complicated and dangerous transseptal catheterization procedures.
b. Background Art
The human heart includes a right ventricle, a right atrium, left ventricle and left atrium. The right atrium is in fluid communication with the superior vena cava and the inferior vena cava. The tricuspid valve separates the right atrium from the right ventricle. The right atrium is separated from the left atrium by the interatrial septum.
A wide variety of diagnostic and therapeutic procedures have been developed in which a catheter is transluminally advanced within a guide sheath or over a guidewire into various chambers and across valves of the heart. The most difficult chamber of the heart to access with a catheter is the left atrium. Access to the left atrium through the pulmonary artery is not possible. Approaches from the left ventricle are difficult, may cause arrhythmias and may present difficulty in obtaining stable catheter positioning. Accordingly, the most common approach used by electrophysiologists to gain access to the left atrium is through puncture of the interatrial septum.
The objectives of left atrial access can be either diagnostic or therapeutic. One therapeutic use is electrophysiological intervention, e.g., left atrial ablation. Catheter ablation involves the placement of energy (typically RF) through a catheter, into various locations of the heart to eradicate inappropriate electrical pathways affecting the heart function. When these locations are in the left atrium, the catheter through which the RF generator is placed typically is itself placed through transseptal catheterization.
In most cases, transseptal catheterization is facilitated with three separate transseptal tools; a sheath, dilator, and a needle. For example, FIG. 1 shows the details of the proximal end of current transseptal tools, which include: a sheath 10 and a sheath hub 12; a dilator 14 and a dilator hub 16; and a needle assembly 22 comprising a needle 18 and needle hub 20. The conventional approach for transseptal catheterization follows a number of steps. First, a guidewire is introduced into the femoral vein (or other pathway of choice) and is manipulated into the superior vena cava (SVC). Second, a sheath 10 typically having a dilator 14 disposed therein are inserted over the proximal end of the guidewire and are fed into the SVC. At this point, the guidewire is removed. Third, a needle assembly 22 (potentially including a stylet 24) is advanced through the inner lumen of the dilator 14 until the distal end of the stylet 24 or needle 18 is just inside the distal end of the dilator 14. The stylet 24 typically extends a portion beyond the distal end of the needle 18.
In most cases, the physician visually determines the point at which the stylet 24 and/or needle assembly 22 is just inside the distal end of the dilator 14 by examining the space between the proximal end of the dilator hub 16 and the distal end of the needle hub 20 (the distance “X” in FIG. 1). As a rule of thumb, it is typically understood that the stylet 24 is in the appropriate position when the dilator hub 16 is separated from the needle hub 20 by “two finger-widths” of the physician. Clearly, this method is an imprecise approximation of the position and lends itself to adjustment errors and difficulties. Alternatively, the physician may use fluoroscopy to verify the position of the stylet 24 or needle 18. This method, however adds significant expense and complications to the procedure.
Once the needle assembly 22 is deemed in the appropriate position, the stylet 24 is typically removed from the inner lumen of the needle 18 and discarded. At this point, the physician then advances the needle assembly 22 forward until the distal end of the needle 18 is just inside the distal end of the dilator 14. As shown in FIG. 1, this distance is again visually determined and approximated by examining the space between the needle hub 20 and the dilator hub 16. Alternatively, the physician may use other complicated diagnostic methods such as fluoroscopy.
In this position, with the needle 18 still contained within the distal end of the dilator 14, the assembly 22 is pulled along the septal wall of the right atrium until it is proximate the fossa ovalis. The needle assembly 22 is then advanced forward by the physician through the dilator 14 to puncture the septal wall. Upon confirmation of the puncture, the dilator 14 and sheath 10 can then be fed through the septal wall over the needle assembly 22, thereby accessing the left atrium.
Despite clinical acceptance of a wide variety of procedures which require access to the left atrium, significant room for improvement remains in the actual access technique and mechanisms designed to facilitate such access. A number of risks, in addition to the risks associated with normal heart catheterization, are inherent in transseptal catheterization. For example, a major risk present stems from the use of known transseptal devices, which typically have a puncture device, or needle, that can be inadvertently exposed during the procedure. For this reason, there is a need to provide a puncture assembly where the puncture device, referred to in the embodiments of the present application as a needle assembly, is safely maintained at a substantially fixed location within the dilator until the assembly is positioned at the puncture point of the septum.
Moreover, the known assemblies are cumbersome and difficult to operate. Thus, a significant drawback with current transseptal tools lies in the fact that the tools are effectively three separate components that operate independently of one another. This independence introduces significant difficulties to a user in that they must all be manipulated, or held in place, independently through manual efforts of the user. It would be highly desirable to provide for a cooperating handle assembly combining these components, with the addition of mechanical safety features, to provide improved safety and utility in connection with accepted medical procedures. In particular, it is desirable to mechanize the process for proper positioning of the needle, dilator, sheath, and stylet during the procedure and to further provide safety features to avoid unnecessary punctures and similar mistakes during operation.